Of course the function calls are not guaranteed to be called in any particular order with this implementation.

for_each_argument([](auto a) { cout << a; }, 1,2,3,4,5)

could print "52431". The order can be guaranteed by expanding the parameter pack expression in a different context, such as that of an array initializer:

int _[] = {(f(std::forward<Args>(args)),0)...};

Also, I see that Sean Parent posted a similar fix:

(void)(int[]){(f(forward<Args>(args)), 0)...};

However his update uses C99 syntax (compound literals). This can be converted to C++:

using arrT = int[];

static_cast<void>(arrT{(f(std::forward<Args>(args)), 0)...});

Note that the original version of for_each_argument can be called when the number of elements in the parameter pack is 0, while this is not possible with the other versions, because it's not possible to initialize zero-length arrays. This can be easily fixed by adding one element in the initializer list. Another solution is to use std::array, which can be zero-length as special case:

std::array<int, sizeof...(Args)>{(f(std::forward<Args>(args)), 0)...};

Of course, whether calling for_each_argument with no arguments in the parameter pack is useful or not is another issue.

Thanks to fold expressions, in C++17 we'll write:

template<typename Fun, typename...T>

Fun for_each(Fun fun, T&&... args)

{

   (fun (forward<T>(args)), ...);

   return fun;

}